---
id: 594810f028c0303b75339acb
title: 100 门
challengeType: 1
forumTopicId: 302217
dashedName: 100-doors
---

# --description--

There are 100 doors in a row that are all initially closed. You make 100 passes by the doors. The first time through, visit every door and 'toggle' the door (if the door is closed, open it; if it is open, close it). The second time, only visit every 2nd door (i.e., door #2, #4, #6, ...) and toggle it. The third time, visit every 3rd door (i.e., door #3, #6, #9, ...), etc., until you only visit the 100th door.

# --instructions--

实现一个函数，以确定最后一次通过后门的状态。 以数组形式返回最终结果，数组中只包含打开的门的门号。

# --hints--

`getFinalOpenedDoors` 应该是一个函数。

```js
assert(typeof getFinalOpenedDoors === 'function');
```

`getFinalOpenedDoors` 应该返回一个数组。

```js
assert(Array.isArray(getFinalOpenedDoors(100)));
```

`getFinalOpenedDoors` 应该产生正确的结果。

```js
assert.deepEqual(getFinalOpenedDoors(100), solution);
```

# --seed--

## --after-user-code--

```js
const solution = [1, 4, 9, 16, 25, 36, 49, 64, 81, 100];
```

## --seed-contents--

```js
function getFinalOpenedDoors(numDoors) {

}
```

# --solutions--

```js
function getFinalOpenedDoors(numDoors) {
  // this is the final pattern (always squares).
  // thus, the most efficient solution simply returns an array of squares up to numDoors).
  const finalState = [];
  let i = 1;
  while (Math.pow(i, 2) <= numDoors) {
    finalState.push(Math.pow(i, 2));
    i++;
  }
  return finalState;
}
```
